The present invention relates to a canister which absorbs and treats an fuel vapor produced from a fuel tank of a vehicle and prevents the same from being released to the open air. More particularly, the invention relates to a canister having a liquefied fuel treating function for preliminarily treating a liquefied fuel.
A conventionally known canister having a liquefied fuel treating function of this type preliminarily treats a liquefied fuel by collecting the liquefied fuel in a liquid storing case 5 having an introducing path 3 communicating with a fuel tank or the like and a purging path 4 communicating with air inlet pipes of an engine or the like, attached to a wall surface 2a of a case main body 2 filled with an adsorbent adsorbing a fuel vapor, as shown in FIG. 14 (see Japanese Unexamined Patent Application Publication No. 9-88739). A relay pipe 6 communicating with the adsorbent projects from the wall surface 2a of the case main body 2. The relay pipe 6 is covered with the liquid storing case 5. The purging path 4 is bent at right angles in the middle, enters the liquid storing case 5, and extends to the proximity of the leading end of the relay pipe 6. A suction pipe 7 for the liquefied fuel is attached to the purging path 4 in the liquid storing case 5. At the attachment position of the suction pipe 7, the axis of the purging path 4 is perpendicular to the axis of the suction pipe 7.
When the pressure of the fuel vapor in the fuel tank exceeds a certain level, the fuel vapor enters the liquid storing case 5 from the introducing path 3 via a hose member 8. The fuel vapor enters the case main body 2 from the relay pipe 6, adsorbed by the adsorbent 1, and discharged from an open air path 9. The fuel liquefied again in the hose member 8 is stored in the liquid storing case 5. When the engine operates and a negative pressure is produced in an air inlet pipe, on the contrary, air is introduced from an open air path 9, and the fuel adsorbed by the adsorbent 1 is separated. Fluids such as air and the separated fuel are fed to the suction pipe 7 via the relay pipe 6 and the purging path 4.
When the fluid passes through the purging path 4, because the throttle 4a is provided in the purging path 4, the liquefied fuel stored in the liquid storing case 5 is sucked up by a suction pipe 7, and a mixture with the separated fuel is sent to the suction pipe side.
In the conventional canister having a liquefied fuel treating function, however, the fluid flowing through the purging path 4 flows in a direction (2) always perpendicular to the sucking direction (1) of the liquefied fuel. As a result, when providing the purging path 4 on the ceiling surface of the canister having the liquefied fuel treating function because of the restrictions on layout, it is necessary to bend the purging path 4 in the middle as shown in FIG. 14. Bending of the purging path 4 results in a larger pressure loss.
The present invention has therefore an object to provide a canister having a liquefied fuel treating function, which permits coping flexibly with restrictions on layout without the need to bend the purging path in the middle.
The present invention will now be described.
The aforementioned problems are solved in the first aspect of the invention by means of a canister having a liquefied fuel treating function, comprising a liquid storing case having an introducing path communicating with a fuel tank and the like, and a purging path communicating with air inlet pipes of an engine and the like; and a sucking path, provided within the liquid storing case, and sucking the liquefied fuel stored in the liquid storing case; which sucks up the liquefied fuel onto the purging path side by use of the flow of a fluid through the purging path; wherein the sucking direction of the liquefied fuel within the sucking path is caused to substantially agree with the flow direction of the fluid in the purging path.
According to this aspect of the invention, when the engine operates, there occurs a negative pressure in the air inlet pipe, and air and the fluid including the fuel vapor separated from the adsorbent by air flows through the purging path. Since the fluid flows from the liquid storing case having a larger path cross-sectional area into the purging path having a smaller path cross-sectional area, the flow velocity is increased at the purging path. This produces a negative pressure in the purging path. The liquefied fuel stored in the liquid storing case is sucked up by this negative pressure, and taken out onto the purging path side. Because the sucking direction of the liquefied fuel in the sucking path substantially agrees with the flow direction of the fluid in the purging path, upward extension of the purging path in parallel with the sucking path permits coping with a restriction on layout requiring provision of the purging path extending upward on the ceiling surface of the canister having the liquefied fuel treating function, without the need to bend the purging path.
In a second aspect of the invention, in the canister having the liquefied fuel treating function of the first aspect of the invention, a throttle enlarging toward the upstream is provided in the purging path; the sucking path is provided in the throttle; and a flow of the fluid is produced between the outer periphery of the sucking path and the inner periphery of the throttle.
According to this aspect of the invention, the fluid flows between the inner periphery of the throttle and the outer periphery of the sucking path, and the liquefied fuel is sucked up through the sucking path. The sucking direction (1) of the liquefied fuel thus substantially agrees with the flow direction (2) of the fluid. The flow velocity of the fluid is increased in the throttle, leading to a larger negative pressure in the purging path, hence to an increase in the sucking force of the liquefied fuel. Furthermore, because the sucking path is provided in the purging path, it is possible to reduce the size of the liquid storing case.
In a third aspect of the invention, in the canister having the liquefied fuel treating function of the second aspect of the invention, the throttle is formed substantially into a conical shape of which the cross-section becomes gradually larger toward the upstream.
According to this aspect of the invention, the throttle never becomes steeply larger toward the upstream, thus reducing the pressure loss through the throttle.
In the fourth aspect of the invention, in the canister having the liquefied fuel treating function of any one of the first to third aspects, an orifice is provided in the sucking path.
According to this aspect of the invention, the flow rate taken out onto the purging path is adjusted by the orifice.
In the fifth aspect of the invention, in the canister having the liquefied fuel treating function of the first aspect, said purging path and said sucking path are adjacent to each other, and said purging path and said sucking path extend in the same direction.